Gas insulated switchgear used in electric-power-related facilities such as substations and power plants is configured with essential devices such as switchgear, buses, current transformers, disconnectors, and voltage transformers arranged in a sealed metal container filled with arc-extinguishing gas such as sulfur hexafluoride (SF6) that exhibits high insulating and arc-extinguishing properties. Gas insulated switchgear is advantageous to air insulated switchgear from the viewpoint of reduced footprint. With the rise of land costs and the like, however, there have been demands for further footprint reduction by arranging the constituent devices in a still more practical manner.
There are different bus types for the gas insulated switchgear, one of which is called a ring bus type. According to the ring bus type, the entire structure is shaped into a ring form by connecting, in series, units in which an instrument current transformer and a disconnector are provided on each side of a breaker, branching line-side devices from each of the units, and connecting the two ends of the serially connected units by a bus. In a device of the ring bus type, if an accident occurs in any of the units, only power transmission and reception lines connected to this unit should be stopped. Because the power transmission and reception can be continued with other units, high reliability can be attained in power supply.
In the ring-bus-type gas insulated switchgear according to Patent Document 1, breaker units are formed with vertical breakers, and current transformers and disconnectors connected to the sides of the breakers by way of horizontal branches (T branches) provided on the top portions of the breakers are formed, and such breaker units are arranged in a direction perpendicular to the T branches. Moreover, these breaker units are connected in series alternately by the first connection bus unit and the second connection bus unit in the form of rectangular waves on a horizontal surface at approximately the same level as the T branch, and the breaker units at the two ends of the alignment direction of the breaker units are connected to each other by a regression bus unit. In addition, the first and second connection bus units that connect the breaker units to one another are connected to line-side units.
Furthermore, in the ring-bus-type gas insulated switchgear according to Patent Document 2, in which breaker units including vertical breakers and disconnectors connected the two ends of each of the breakers and lead line units including line-side devices are alternately connected in the form of rectangles, the breaker units and the lead line units are arranged outside the rectangular line.
Patent Document 1: International Publication Pamphlet No. WO 01/024333    Patent Document 2: Japanese Patent Application Laid-open No. 2-254908